Field of the Invention
The present invention relates to a stereoscopic image display device, and more particularly, to a stereoscopic image display device, which may implement high-speed eye-tracking techniques using a low-speed camera, and an eye-tracking method thereof.
Discussion of the Related Art
Stereoscopic image display devices, designed to display a realistic 3-dimensional (3D) image, have been applied to a variety of fields including medicine, education, games, movies, televisions, and the like. Such a stereoscopic image display device displays a left-eye image and a right-eye image separate from each other in terms of space or time to cause a viewer to perceive 3D effects from binocular parallax images.
Representative methods to display a 3D image include a glasses method using special glasses and a non-glasses method not using special glasses. In the glasses method, a display device displays a left-eye image and a right-eye image by changing polarization of the images or by separating the images from each other in a time division manner, and a viewer perceives 3D effects using polarized glasses or liquid-crystal shutter glasses. In the non-glasses method, a display device displays a 3D image using optical filters installed to a front or rear face thereof, such as a lenticular sheet, a parallax barrier, and the like.
More specifically, a non-glasses type stereoscopic image display device includes an image panel to display an image, and a switchable panel disposed at the front or rear side of the image panel to spatially separate a left-eye image and a right-eye image from each other by varying a barrier position or a lens position per the left-eye image and the right-eye image.
In addition, the stereoscopic image display device utilizes eye-tracking techniques, which detects the face of a viewer from an image input via a camera mounted to the image panel, and subsequently detects eye position information of the viewer relative to the stereoscopic image display device (e.g., X, Y, and Z coordinates), and display a 3D image while tracking a position of the viewer who is moving by varying a barrier position or a lens position of the switchable panel based on the detected eye position information of the viewer.
Conventionally, the stereoscopic image display device synchronizes update of position information of the viewer with a drive frequency (image capture speed) of the camera. However, the camera is driven at a lower speed than a drive frequency of the switchable panel, and thus position information of the viewer is updated at a lower speed than the drive frequency of the switchable panel, which makes it impossible to display a 3D image accurately conforming to a position of the viewer who is moving. Although this problem may be solved by using a camera having a high drive frequency, a low-speed camera is generally used because of restrictions in terms of price and size of the camera.